Ok... I did some data gathering. The sheets are pretty self explanatory, but there seems to be an issue with the procs of pve power/dmg, getting someway in the way of the each others procs.
http://sdrv.ms/16w4Mvb
The "clean" sheets are just the proc information.
Towards the top of the clean sheets show which relics were used, fight duration and proc counts/avg.
All the tests were continuous fights on a ops dummy on my ship.
You can see this on sheet "1-clean". Sort by time ascending and look at the time between procs.. (filter the "remove effect" from power surge to see this better)
So it seems that 2 criteria is being applied to the power proc relic... 20 secs and 4.5 secs from the last damage proc.
You will see like results on sheet "3-clean" and "4-clean" as well.
The problem with this is that you can get extremely long reprocs from the power proc relic.